System and method for remotely detecting and locating faults in a power system

ABSTRACT

A system and method are provided for remotely detecting and locating faults in a power system. The system includes at least one slave controller and at least one supplemental protection module. The slave controller is disposed proximate at least one load and electrically connected to the loads via at least one conductor. More particularly, the slave controller includes at least one solid-state switch capable of controllably altering the input current to the loads. The slave controller also includes at least one measuring element for measuring at least one parameter associated with the loads and the solid-state switches. The solid-state switch can then controllably alter the input current to the loads according to the parameter. The supplemental protection modules are electrically connected to the conductors between the slave controller and the loads. In this regard, the supplemental protection modules can detects at least one fault in at least one conductor.

FIELD OF THE INVENTION

The present invention relates generally to power system maintenance and,more particularly, to a system and method for remotely detecting andlocating faults in a power system.

BACKGROUND OF THE INVENTION

In many industries today, such as the avionics and automotiveindustries, complex and costly electrical components, systems andsubsystems, as well as the electrical power systems powering thesecomponents, are interconnected by many bundles of conductors, typicallywires, with each bundle including a plurality of wires. Although eachwire is typically surrounded by insulation, or sheathing, such wires canbecome faulty. In this regard, as the wires age, the insulation canbreakdown and chaff. In such instances, the wires can contact otherwires or other conductive structures, such as framework. Also, strandsin aging wires can begin to separate and tear due to vibration, shockand stress on the wires. Stress due to pinching, rubbing, moisture,corrosion, excessive heat and/or lightening strikes also pose risks thatcan lead to wire damage. Further, tight fitting connection points withinconnectors can loosen over time when subjected to the same environmentalconditions as the conductors, and when subjected to numerous connectsand disconnects due to replacement and maintenance of the electricalcomponents, systems, subsystems, and the electrical power systems.

As will be appreciated by those skilled in the art, when the insulationsurrounding the wires breaks down or chaffs, or the wire otherwisebecomes faulty, undesirable electric arcs or other wire breakdown canoccur at one or more locations along the wires, which can lead to breaksor shorts in the system. It will also be appreciated that in manyinstances, the location of such arc events or other wire breakdowns canbe difficult to find. In this regard, the location of an arc event orother wire breakdown may be inside of a bulkhead or inside of a wirebundle. Also, an arc event may only brown an area of occurrence withoutactually burning through or burning the insulation away form theaffected wire.

In many instances, detecting and locating the arc event or other wirebreakdown can be difficult, if not impossible. In this regard, detectinga fault in the system as being caused by a faulty wire may be difficultin systems that also include complex electrical components, systems,subsystems and power systems. As such, misdiagnosing a fault in thesystem as being caused by costly electrical components, for example, canresult in unnecessary replacement of such components while still failingto correct the fault.

In addition to the difficulty in detecting an arc event or other wirebreakdown, locating such an arc event or other breakdown is alsodifficult. In many instances, the location of the arc event or otherbreakdown may be in a location that is impossible to visually locatewithout extracting a wire bundle from the system. However, inspection ofmany feet of wire within a system can be very time consuming, and insome cases, may place maintenance personnel at risk for injury. Also,most conventional wire testing equipment is cumbersome and requiresunique training of maintenance personnel as to how to use the equipment.Use of such equipment also requires that one or more wire bundles bedisconnected in order to test the wires. Unnecessary removal ofequipment can also be very costly and time consuming, however, and canadd to the required time to perform maintenance on the system. Further,many times such connection points are not located in easily accessedlocations.

SUMMARY OF THE INVENTION

In light of the foregoing background, the present invention provides asystem and method of locating faults in a power system. The system andmethod of embodiments of the present invention are capable of detectingany of a number of different faults including, for example, damagedconductors, arc fault events and short circuits. In this regard, thesystem and method of embodiments of the present invention are capable ofpreventing interference to loads during operation by conducting a teston a “dead conductor” before applying power to the load. By pre-testingthe wire/load before power is applied, it is possible to prevent powerfrom being applied to a damaged wire/load and may avert an arc eventfrom occurring. The system and method of embodiments of the presentinvention may further provide the location of damage in a conductor,such as the location of a suspected arc event. By locating the suspecteddamage, maintenance personnel may advantageously narrow the search forthe damage to a specific location, even internal to a wiring bundle,without having to spend countless hours visually inspecting every wirefrom one end to the other.

The system and method of embodiments of the present invention may alsomonitor input current to the loads for abnormal current representativeof an arc fault event and/or a short circuit. The system and method ofembodiments of the present invention are capable of continuouslymonitoring current to the loads for an arc fault event and/or shortcircuit such that, upon detection of such an event, current to therespective loads can be shut off, thereby reducing the likelihood of thearc fault event becoming catastrophic. Once shutoff, then, the systemand method of embodiments of the present invention are capable ofverifying the arc fault event and/or short circuit, and may also becapable of locating the arc fault event and/or short circuit. In thisregard, the arc fault event is typically verified before the system andmethod of embodiments of the present invention attempt to locate the arcfault event.

According to one aspect of the present invention, a system is providedfor remotely detecting and locating faults in a power system. The systemincludes at least one slave controller and at least one supplementalprotection module. The slave controller is disposed proximate at leastone load and electrically connected to the loads via at least oneconductor. More particularly, the slave controller includes at least onesolid-state switch capable of controllably altering the input current tothe loads. The slave controller also includes at least one measuringelement for measuring at least one parameter, such as at least onecurrent parameter, associated with the loads and the solid-stateswitches. The solid-state switch can then controllably alter the inputcurrent to the loads according to the parameter.

The supplemental protection modules are electrically connected to theconductors between the slave controller and the loads. In this regard,the supplemental protection modules are capable of detecting at leastone fault in at least one conductor. Then, when the supplementalprotection module detects a fault, the supplemental protection modulecan notify a respective slave controller such that the solid-stateswitches of the respective slave controller can alter the input currentto the loads. In one embodiment, the solid-state switches can operate inan on mode where the solid-state switches permit a respective load toreceive the input current, and/or an off mode where the solid-stateswitches prevent the respective load from receiving the input current.When the solid-state switches operate in the off mode, the supplementalprotection modules are capable of testing the conductors before thesolid-state switches are placed in the on mode to thereby detect atleast one fault.

The supplemental protection modules can detect a number of differentfaults in the power system. For example, each supplemental protectionmodule can be capable of detecting at least one damaged conductor. Inthis regard, the supplemental protection module can detect the damagedconductor by transmitting at least one test pulse along at least onerespective conductor and receiving at least one reflection from therespective conductors. Thereafter, the supplemental protection modulecan compare the reflections to reference data to thereby detect and/orlocate at least one damaged conductor. The supplemental protectionmodule can be further capable of detecting at least one damagedconductor by converting the reflected signal to digital datarepresentative of the reflections that can then be compared to referencedata, such as previously stored reference data.

Each supplemental protection module can also be capable of determining alength of the conductors based upon at least one transit time betweentransmission of the test pulses and reception of the respectivereflections. Each supplemental protection module can then be capable ofcomparing the reflections to reference data by comparing the determinedlengths to at least one reference length. More particularly, then, atleast one damaged conductor can be detected when at least one determinedlength is shorter than the respective reference length by more than athreshold length. Each supplemental protection module can then becapable of locating the damage as a point on the respective conductor atthe determined length.

In addition to, or in lieu of, detecting a damaged conductor, eachsupplemental protection module can be capable of detecting an electricarc event by detecting white noise and/or chaotic behavior in currentthrough the at least one conductor to the at least one load. In thisregard, each supplemental protection module can be capable of detectingwhite noise by detecting a spectrally dense current through theconductors to the loads. Each supplemental protection module can befurther capable of detecting at least one fault comprising at least oneabnormal current representative of a short circuit (e.g., a ground faultas opposed to a conductor-to-conductor short circuit), and/or anelectric arc event. More particularly as to detecting a short circuit,in various embodiments each conductor comprises a pair of conductors.Each supplemental protection element can then be capable of detecting atleast one fault by receiving a measurement representative of a currentdifference in the pair of conductors, and thereafter comparing themeasurement to a predefined threshold. In this regard, the supplementalprotection element is capable of detecting an abnormal currentrepresentative of a short circuit when the measurement is greater thanthe predefined threshold.

When the supplemental protection module detects an electric arc eventand/or a short circuit, the supplemental protection module can notify arespective slave controller such that the solid-state switches of therespective slave controller can alter the input current to the loads toprevent the respective loads from receiving the input current. Also,when the respective slave controller alters the input current to preventthe respective load from receiving the input current, the respectivesupplemental protection module can verify the electric arc event and/orlocate the electric arc event on the respective conductor. In thisregard, the respective supplemental protection module is typicallycapable of verifying the electric arc while the electric arc is present,if the supplemental protection module has detected an electric arc.

A method of remotely detecting at least one fault in a power system isalso provided.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a block diagram of a system of remotely controlling at leastone load according to one embodiment of the present invention;

FIG. 2 is a block diagram of a supplemental protection module accordingto one embodiment of the present invention;

FIG. 3 is a block diagram of an arc fault detector according to oneembodiment of the present invention;

FIG. 4 is a block diagram of a damaged wire detector according to oneembodiment of the present invention;

FIG. 5 is a block diagram of a ground fault circuit interrupt accordingto one embodiment of the present invention;

FIG. 6 is a block diagram of a supplemental protection module includingan integrated arc fault detector, damaged wire detector and ground faultcircuit interrupt according to one embodiment of the present invention;

FIG. 7 is a block diagram of a programmable controller including asingle solid-state switch and multiple measuring devices according toone embodiment;

FIG. 8 is a block diagram of a solid-state switch according to oneembodiment of the present invention;

FIG. 9 is a graph illustrating a characteristic trip curve for arespective load and several current parameter measurements for therespective load; and

FIGS. 10A, 10B and 10C are flow charts of a method of remotelycontrolling an input current from a master controller through at leastone switch to at least one load according to one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

FIG. 1 is an illustration of a system that would benefit from thedamaged wire detector of one embodiment of the present invention. Thisillustration is provided so that a more complete understanding of thepresent invention may be appreciated. It must be understood that thepresent invention is not limited to this configuration and may beembodied in many different power systems.

With regard to FIG. 1, a general embodiment of a power system in whichthe present invention is used is shown. The system, typically used topower devices onboard airplanes and automobiles, includes a programmablecontroller (i.e., slave controller) 10 disposed proximate andelectrically connected to at least one load 14, such as one or moreelectrical components, systems and/or subsystems. For example, theprogrammable controller can be used to drive electric motors and servos,therefore replacing high maintenance hydraulic devices. The programmablecontroller can provide either alternating current (AC) current andvoltage or direct current (DC) current and voltage to the loads,depending upon operation of the loads. As shown and described herein,however, the programmable controller is particularly adapted to provideDC current and voltage to the loads. But it should be understood thatthe programmable controller can equally provide AC current and voltageto one or more loads, as desired.

The programmable controller 10 can be electrically connected to theloads 14 via electrical conductors, such as copper wires or the like. Byusing one programmable controller to control multiple loads, and bydisposing the controller proximate the loads as opposed to in onecentral, humanly accessible location, cabling in the system is reducedwhich, in turn, reduces wire losses in the system, and reduces theweight of the system. The programmable controller can be electricallyconnected to a remote master controller 12, such as a high-levelprocessor or computer, which controls the input current to the loadsthrough the programmable controller. Although the programmablecontroller can be electrically connected to the master controller, theprogrammable controller can additionally, or alternatively, beconfigured to operate independent of the master controller or any othertype of controller.

Electrically connected between the programmable controller 10 and theloads 14, the system includes a supplemental protection module 16. Thesupplemental protection module is capable of monitoring the currentoutput of the programmable controller for conditions conducive to anelectric arc event. In addition, the supplemental protection module iscapable of monitoring the impedance conditions associated with theconductors connecting the programmable controller, as well as with theloads. By monitoring the conductors, as well as the current from theprogrammable controller, the programmable controller can be operated toprevent power from being applied across a damaged conductor or load, aswell as to prevent the creation of an arc event.

The programmable controller 10 and the remote master controller 12 caneach draw power from a variety of sources as such are known to thoseskilled in the art. For example, in devices such as airplanes andautomobiles, the programmable controller and remote master controller,in addition to the loads 14, can draw power from the device's existingpower bus. Additionally, or alternatively, the programmable controllerand/or master controller can be connected to a stand-alone power sourcethat supplies power to the programmable controller and/or mastercontroller. The master controller of the system can additionally beconnected to various other electrical systems within various devices.For example, in the automotive industry, the master controller caninterface with the vehicle management system and carry out the vehiclemanagement system instructions to the loads in an autonomous fashion. Itshould be understood that, although the system illustrated depicts oneprogrammable controller electrically connected to one master controller,a single master controller can be, and preferably is, electricallyconnected to multiple remote programmable controllers without departingfrom the spirit and scope of the present invention. In turn, asupplemental protection module 16 can be, and preferably is,electrically connected between each programmable controller and theloads connected to the respective programmable controller.

As previously mentioned, the master controller 12 controls the inputcurrent to the loads 14 through the programmable controller 10. As such,the programmable controller can be used as a power relay or a circuitbreaker, depending upon the desired application and the types of loadsconnected. As discussed below with reference to the programmablecontroller controlling the loads, the master controller controls theprogrammable controller by continuously monitoring the programmablecontroller, controlling the output current from the programmablecontroller to the loads such as in on and off modes, selecting thevarious system parameters such as current, voltage and temperaturelimits, and programming the various system parameters into theprogrammable controller. Alternatively, or additionally, theprogrammable controller can be preprogrammed before integration into adevice and run free from control from the master controller. Therefore,throughout the description of the present invention, reference will onlybe made to the programmable controller. But it should be understood thatthe control features of the programmable controller can be performed bythe master controller and/or the programmable controller. For moreinformation on such a programmable controller, see U.S. patentapplication Ser. No. 09/842,967, entitled: Programmable Controller ForRemotely Controlling Input Power Through a Switch to a Load and anAssociated Method of Operation, filed Apr. 26, 2001, the contents ofwhich are hereby incorporated by reference in its entirety.

Referring now to FIG. 2, in one embodiment, the supplemental protectionmodule 16 includes an arc fault detector 16 a, a damaged wire detector16 b, and can additionally include a ground fault circuit interrupt 16c. The arc fault detector is capable of monitoring the current flowthrough the programmable controller for anomalies associated with an arcevent. The arc fault detector can monitor the current flow at any time,but in one embodiment, monitors the current flow after or while theprogrammable controller applies power to the loads. In this regard, thearc fault detector can monitor current flow through the programmablecontroller after power has been applied, or as power is applied, to theloads to attempt to detect an arc event before widespread damage occursin the system.

The damaged wire detector 16 b is capable of monitoring the impedanceconditions associated with the conductors connecting the programmablecontroller 10 to the loads, as well as the loads 14. Typically, theconductors are tested before applying power to the loads to therebyprevent malfunction in the system upon applying power to the loads. Thedamaged wire detector can detect a damaged wire and attempt to locatethe damage in any of a number of different manners, such as according toa time domain reflectometry technique, as described below. The groundfault circuit interrupt 16 c, which may or may not be integrated withinthe damaged wire detector, is capable of monitoring for stray currentsor otherwise abnormal currents on the conductors that may indicate aground fault in one of the conductors and/or an electric arc event, suchas from a conductor to ground.

Reference is now drawn to FIG. 3, which illustrates a schematic blockdiagram of an arc fault detector 16 a according to one embodiment of thepresent invention. Generally, an arc, as are most natural events, iscomposed of 1/f (pink) noise at low frequencies and white noise athigher frequencies. The arc fault detector, then, is capable ofmonitoring the output current from the programmable controller 10 forwhite noise of sufficient amplitude, which may be indicative of an arcevent. For example, the arc fault detector can monitor the outputcurrent for amplitudes that exceed background noise by a predefinedthreshold. White noise may be defined as high spectral density(characterized by a multitude of frequency content), with a signalstrength approximately equal in the same bandwidth irrespective of therespective frequency examined. In addition, arc events can becharacterized by chaotic behavior in signal strength. Thus, the arcfault detector, is further capable of monitoring the output current fromthe programmable controller for chaotic behavior which, along with thewhite noise, may characterize an electric arc event.

The arc fault detector 16 a can include a processing element 18 capableof controlling operation of an arc fault detection module 20, which maycomprise analog circuit elements such as operational amplifiers, filtersand comparators, as described more fully below. In this regard, the arcfault detector can include an oscillator 21 capable of driving theprocessing element to operate the arc fault detection module. Theprocessing element is capable of signal processing a narrow band ofcurrent in the audio region while attempting to locate characteristicsof an arc event. For example, the processing element can process theaudio region to monitor the spectral density of the current incombination with chaotic amplitude changes. If high spectraldensity/chaotic amplitude changes are detected, the processing elementcan inform the programmable controller 10 which, in turn, can preventcurrent from being passed to the loads, as described more fully below.In this regard, current having a high spectral density can be defined asthat current with at least a portion present in all frequencies. Also,current with chaotic amplitude can be defined as that current lacking apattern repetition.

In the embodiment shown in FIG. 3, the arc fault detection module 20 caninclude a front-end high pass filter/gain stage 22 that feeds the outputcurrent (IANA) from the programmable controller 10 to a switchableband-pass filter 24. The high pass filter/gain stage can comprise any ofa number of different high pass filters, such as a 8 kHz, 3 pole highpass filter. The high pass filter/gain stage is capable of attenuatingstrong load related components, such 60 and 400 Hz fundamentals andtheir associated harmonics when the programmable controller provides ACcurrent and voltage to the loads, and capable of attenuating DC and lowfrequency switching currents when the programmable controller providesDC current and voltage to the loads. By attenuating strong load relatedcomponents, the high pass filter/gain stage can prevent the outputcurrent from driving the signals to the voltage rails of the othercomponents in the arc fault detection module, as described below. Thehigh pass filter/gain stage also provides some gain to signals above apredefined frequency (e.g., 8 kHz) to thereby facilitate detecting smallarc fault characteristics in the output current.

The band-pass filter 24 can comprise a state-variable analog filter,such as a 4 pole band-pass filter, having any of a number of bandwidthswith any of a number of different selectable center frequency ranges. Inone embodiment, for example, the band-pass filter has a bandwidth ofapproximately 500 Hz, and has a center frequency selectable between 8and 21 kHz. The processing element 18 can select the center frequency ofthe band-pass filter, such as by passing a digital center frequencyselection through a digital-to-analog (D/A) converter 26. The centerfrequency is advantageously selectable such that the processing elementcan monitor for characteristics that are indicative of electric arcs inall bandwidths, such as across the entire upper audio region. In thisregard, the band-pass filter slices out a spectrum of the output currentfrom the programmable controller 10 within which to monitor forcharacteristics that lead to an electric arc. And because an electricarc is spectrally dense, its presence will typically be identifiable inthe audio range without interference from high frequency noise.

The output from the band-pass filter 24 can be fed into another gainstage 28, which can pass the output to a current-differencing amplifier(CDA) 30, a threshold detector 32 (described below) and a zero-crossingcomparator 34 (described below). Advantageously, the CDA of oneembodiment includes a diode front-end, which allows the CDA to operateas a very effective non-linear amplifier. In this regard, the CDA cangenerate sum and difference products. In other terms, the CDA cangenerate harmonics for sine and other than pure sine waves. However, ifa signal is in a bandwidth between a lower frequency and a higherfrequency, is complex and has spectral density, the output of the CDAcan consist of all frequencies between 0 and the difference between thehigher and lower frequencies due to the difference. Similarly, theoutput of the CDA can also consist of all frequencies between two timesthe lower frequency and the sum of the higher and lower frequencies dueto the sum. For example, for a signal in the bandwidth between 8 and 9kHz that is complex and has spectral density, the output can consist ofall frequencies between 0 and 1 kHz due to the difference, and allfrequencies between 16 and 17 kHz due to the sum.

The output of the CDA 30 can be AC coupled to remove any DC bias andthen passed through a low pass filter 36, such as an analog 500 Hz lowpass filter. The low pass filter can pass only the signal due to thedifference, as processing the signal due to the difference is sufficientto monitor for spectral density. It will be appreciated, however, thatthe amplitude of the signal due to the difference is not a measure ofspectral density. To measure spectral density in the arc fault detectionmodule 20 would require a very narrow band filter in place of the lowpass filter to monitor for tight difference frequencies. Such a narrowband filter would add complexity to the arc fault detector 16, however,and still not guarantee spectral density as just two slightly separatedfrequencies could produce the output.

The output from the low pass filter 36 is therefore passed throughanother zero-crossing comparator 37, which can have some hysteresis andreference offset (Vref). Thereafter, the processing element 18 can taketiming measurements of the pulse edge-to-edge “scattering” within acertain time period (e.g., 20 msec) to determine, and be certain of, thepresence of frequencies in a specified band (e.g., 0 to 500 Hz). Fromthe timing measurements, then, an arc event can be detected, such as byreviewing the measurements within the time period to determine whetherthe time between pulse edges and/or the width of the pulses vary in arandom pattern. In addition to passing the output of the low pass filterto comparator 37, the output of the low pass filter can also be passedas an analog signal (MIXANA) to the processing element. The processingelement, in turn, can monitor the output for chaotic amplitude behavior.In this regard, the low frequency of the output signal facilitates theprocessing element finding and comparing the local peaks to determine ifa chaotic pattern exists between the peaks.

As indicated above, gain stage 28 can pass the output from band-passfilter 24 to threshold detector 32 and comparator 34. The thresholddetector, which can comprise a precision rectifier, is capable ofmeasuring the signal strength in the selected frequency band of theband-pass filter. In this regard, if the signal strength exceeds acertain threshold level in each bandwidth, an electric arc may bepresent in the signal. From the threshold detector, the signal strengthcan be low pass filtered (not shown), and thereafter input to theprocessing element 18 as an analog signal (THRESDET).

Comparator 34 also receives the output from the band-pass filter 24, andthereafter passes the output to the processing element 18. Comparator34, which can have some hysteresis and reference offset (Vref), allowsthe processing element to make timing measurements between pulse edgeswithin the selected frequency band. In this regard, the processingelement can control operation of the comparators 34, 37 via strobesignals (STROBE A and STROBE B) to each comparator. Spectral densitywill typically be evident in each band during an electric arc event. Forexample, spectral density can be determined from examining the zerocrossings from the output of the gain stage 28. In this regard, if anelectric arc having a very wide-band spectrum is band-pass filtered(utilizing band-pass filter 24), such as from 2 to 4 kHz, zero crossingsfrom between 0.25 ms and 0.125 ms would be apparent. The output of theband-pass filter can be amplified (utilizing gain stage 28) to the pointof clipping to make a 0 to 5 volt signal swing. The processing elementcan then count the time between the zero crossings for a period ofapproximately 50 ms, or about 100 samples. Thereafter, the processingelement can make timing measurements to check for a completely randompattern of the zero-crossings at all possible time intervals. As will beappreciated, a non-spectrally dense signal, like a square wave, wouldnot pass such a test, even though the square wave has a lot of frequencycontent with the square wave's odd harmonics.

The processing element 18 is also capable of communicating with theprogrammable controller 10. In this regard, the programmable controllercan clock data into and out of the processing element, such as the datautilized by the processing element to determine if an electric arc eventis occurring, utilizing signal lines AFD CLOCK and AFD DATA as shown inFIG. 3. In addition, the processing element can transmit a notification,alert or the like to the programmable controller, such as when theprocessing element detects an electric arc event. As shown in FIG. 3,then, such a notification, alert or the like can be transmitted to theprogrammable controller utilizing the FAULT ALERT signal line. For moreinformation on such an arc fault detector, see U.S. patent applicationSer. No. 10/662,565, entitled: System, Arc Fault Detector and Method forRemotely Detecting and Locating Electric Arc Fault Events in A PowerSystem, filed Sep. 15, 2003, the contents of which are herebyincorporated by reference in its entirety.

Reference is now drawn to FIG. 4, which illustrates a schematic blockdiagram of a damaged wire detector 16 b according to one embodiment ofthe present invention. The damaged wire detector includes a processingelement 40 capable of controlling operation of a time domainreflectometry (TDR) module 42. As described more fully below, theprocessing element can be capable of transmitting signals onto theconductors between the programmable controller 10 and the loads 14, andreceiving digital data representative of signals reflected back from theconductors. In this regard, the damaged wire detector can include anoscillator 43 capable of driving the processing element to transmitsignals and receive the digital data.

In addition to the processing element and oscillator 43, the damagedwire detector can include an isolation transformer 44 capable ofinjecting a pulse onto the output. The TDR module is capable oftransmitting a series of test pulses down the conductors connecting theprogrammable controller 10 and the loads 14. Each test pulse canpropagate down the conductors and, at a termination point, reflect backto the TDR module, which can receive the reflection and thereaftergenerate digital data representative of the reflection. Thereafter, theprocessing element 40 can analyze the digital data to determine if aconductor is damaged and attempt to identify a location of the damage.

More particularly, the TDR module 42 can comprise a driver 46 throughwhich each test pulse is driven onto the conductors via the isolationtransformer 44. The test pulse can comprise any of a number of differentpredetermined pulses, such as a 1 microsecond, 5 volt analog pulse. Ifdesired, the test pulse can be passed through a resistor, such as a 25Ohm resistor, before passing through the transformer to thereby give thedriver an output impedance that forms a divider with the conductorimpedance. Upon receiving the reflection back from the conductors viathe transformer, the analog reflection can be converted to digital datarepresentative of the reflection by passing through a comparator 68,which compares the analog reflection to an analog pulse width modulated(PWM) controlled DC threshold signal, as such will be appreciated bythose skilled in the art.

To allow the TDR module 42 to receive reflections of differentmagnitudes to thereby detect termination points of different magnitudesand at different lengths along the conductors, the reflection from eachtest pulse can be converted to digital data with different thresholds.For example, the reflections can be converted to digital data withdifferent thresholds by comparing the reflections to a DC thresholdlevel reference generated from an adjustable PWM signal. In this regard,the magnitude of the threshold signal, and thus the threshold of theresulting digital data, can be set by a level adjust element 50. Also,before passing through the level adjust element, the threshold signalcan be filtered, such as by filter 52, which can comprise any of anumber of different conventional electrical elements, such as resistors52 a, capacitors 52 b or the like. In this regard, the threshold signalcan be filtered to generate the DC threshold level reference. The DCthreshold level reference can then be scaled and offset to producethreshold level settings for the comparator 68. The threshold levelsettings can comprise any of a number of different levels, but in oneembodiment, the threshold signals range from +7 volts to −7 volts inapproximately 0.78 volt increments.

After converting the analog reflections to digital data representativeof the reflections, the digital data can be passed to the processingelement 40 for analysis to determine if a conductor is damaged andattempt to identify a location of the damage. The digital data can bepassed to the processing element in any of a number of differentmanners, such as by being passed directly to the processing element. Ina more typical embodiment, however, the digital data is passed to abuffer, such as a first-in-first-out (FIFO) buffer 54, which thereafterpasses the digital data to the processing element. The FIFO buffer cancomprise any of a number of known FIFO buffers, such as a 512×1 FIFObuffer. The FIFO buffer permits the processing element 18 to receive thedigital data at a lower rate than which it was generated. Operation ofthe FIFO can be controlled by an oscillator 56 that, in turn, iscontrolled by the processing element. In this regard, receipt of theprocessing element of the digital data can be controlled by controllingthe oscillator. As such, the processing element can enable operation ofthe TDR module 42 via control of the oscillator.

The oscillator 56 can clock the digital data into the FIFO buffer 54from the comparator 48 at any of a number of different rates such as,for example, at 100 MHz. In this regard, a rate of 100 MHz provides 10nano-second timing resolution, or on the order of one or two meterdistance resolution for typical conductors. Similarly, the oscillatorcan clock the digital data from the FIFO buffer to the processingelement 40 at any of a number of different rates. In addition to passingthe digital data to the processing element, the FIFO buffer can alsooutput the clock signal from the oscillator 56 to the processingelement. In this regard, the processing element can receive the digitaldata and associated clock signals such that the processing element cansynchronize the digital data with reference data for comparison todetermine if the conductors are damaged.

More particularly, the processing element 40 can compare the digitaldata with reference data in memory to determine if the conductors aredamaged. As will be appreciated by those skilled in the art, accordingto the time domain reflectometry technique, as the test pulses aretransmitted down the conductors, all or part of the pulse energy isreflected back along the conductors when the pulses reach the end of theconductor or reach damage along the length of the conductor. Theprocessing element can then measure the time required for each testpulse to travel down the conductors and reflect back, and convert thetime to distance, which is thereafter compared to a reference length.The reference length can be determined in any number of differentmanners, such as from the reference data. The reference data, in turn,can comprise data stored in memory, such as during “calibration” of theTDR module 42. In this regard, the TDR module can be calibrated by, forexample, collecting the reference data as the results of the testing aknown good conductor/load. As will be appreciated, distances determinedfrom the digital data that are significantly shorter than correspondingdistances determined from the reference data can be regarded aslocations of damage along the length of the conductors. The differencesbetween the distances determined from the digital data and thecorresponding distances determined from the reference data required toindicate a location of damage can be selected in any of a number ofdifferent manners to provide any of a number of different levels oftolerance of the system. For example, the difference required toindicate the location of damage can be selected to be greater than fivepercent of the distance determined from the reference data.

The processing element 40 is capable of communicating with theprogrammable controller 10. In this regard, the programmable controllercan clock data into and out of the processing element, such as distancesdetermined from the digital data and/or the reference data, utilizingsignal lines TDR CLOCK and TDR DATA as shown in FIG. 4. In addition, theprocessing element can transmit a notification, alert or the like to theprogrammable controller, such as when the differences between thedistances determined from the digital data and the correspondingdistances determined from the reference data required to indicate alocation of damage exceed a threshold, as described more fully below. Asshown in FIG. 2, then, such a notification, alert or the like can betransmitted to the programmable controller utilizing the FAULT ALERTsignal line. For more information on such a damaged wire detector, seeU.S. patent application Ser. No. 10/663,600, entitled: System, DamagedWire Detector and Method for Remotely Detecting and Locating DamagedConductors in A Power System, filed concurrently herewith, the contentsof which are hereby incorporated by reference in their entirety.

Referring to FIG. 5, a ground fault circuit interrupt 16 c is shownaccording to one embodiment of the present invention. As shown, theground fault circuit interrupt includes a processing element 58 capableof driving a ground fault circuit interrupt module 60 to monitor theconductors for stray currents that may indicate a short circuit toground in one of the conductors and/or an electric arc event to ground.Like in the arc fault detector 16 a and the damaged wire detector 16 b,the ground fault circuit interrupt can include an oscillator 61 capableof driving the processing element to monitor the conductors. The groundfault circuit interrupt module can comprise any of a number of knownanalog elements, such as operational amplifiers, comparators and thelike, capable of detecting a difference in the currents in the pair ofconductors (Vout and RTN), which may indicate a short circuit and/or anelectric arc event.

The ground fault circuit interrupt module 60 is capable of receiving apulse signal, such as a 100 kHz pulse (i.e., GFC 100 kHz), from theprocessing element 58. With each pulse, then, the ground fault circuitinterrupt module can receive a measurement representative of the currentdifference between the pair of conductors to the loads, as such may bedetermined by passing the currents through the core of a sensingtransformer 62. As will be appreciated by those skilled in the art, theconductors can pass through the core of the sensing transformer so thatthe currents in the conductors at any instant are flowing in opposingdirections. If the currents in the conductors are exactly equal, then, anet magnetic flux of zero will be affected in the core. A non-zero netcurrent in the conductors, however, can bias the transformer towardsaturation. At any current difference, then, the secondary outputvoltage of the transformer can be representative of the currentdifference in the conductors, as opposed to the pulse level driven ontothe primary of the transformer.

Like with the arc fault detector 16 a and the damaged wire detector 16b, the processing element 58 of the ground fault circuit interruptmodule 60 is capable of communicating with the programmable controller10. In this regard, the programmable controller can clock data into andout of the processing element, utilizing signal lines GFI CLOCK and GFIDATA as shown in FIG. 5. In addition, when the current difference in theconductors exceeds a predefined threshold, the ground fault circuitinterrupt module 60 can transmit a notification to the processingelement (GNDFAULT), which can thereafter notify the programmablecontroller 10. In turn, the programmable controller can operate toprevent current from reaching the loads 14, as described more fullybelow. The predefined threshold can be set in any of a number of mannersbut, in one embodiment, the threshold is set at approximately 4-6 mA. Toverify a short circuit and/or arc event after operating the programmablecontroller to prevent current from reaching the loads, the damaged wiredetector can test the conductors, such as by transmitting test pulsesdown the conductors and receiving, and thereafter analyzing, reflectionsreceived from the conductors, as indicated above and described morefully below.

As shown in FIGS. 3, 4 and 5, each of the arc fault detector 16 a,damaged wire detector 16 b and ground fault circuit interrupt 16 c ofthe supplemental protection module 16 can each include a processingelement 18, 40 and 58, respectively. As will be appreciated by thoseskilled in the art, one or more of the elements of the supplementalprotection module can include the same processing element withoutdeparting from the spirit and scope of the present invention. Forexample, as shown in FIG. 6, the processing elements of the arc faultdetector, the damaged wire detector and the ground fault circuitinterrupt can be embodied in a single supplemental protection processingelement 64, with oscillators 21, 43 and 61 embodied in a singleoscillator 65. In such an embodiment, the supplemental protection modulecomprises the supplemental protection processing element, theoscillator, and additionally includes the remaining elements of the arcfault detector, the damaged wire detector and the ground fault circuitinterrupt. More particularly, the supplemental protection module furtherincludes the ground fault circuit interrupt (GFCI) module 60, thesensing transformer 62, the TDR module 42, the isolation transformer 44and the arc fault detection module 20. As will be appreciated, in suchan embodiment, the single supplemental protection element processingelement can communicate with the programmable controller 10 such as toclock data into and out of the supplemental protection elementprocessing element utilizing signal lines SPI CLOCK and SPI DATA.

Referring now to FIG. 7, the programmable controller 10 of oneembodiment of the present invention includes a controller processingelement 66. The controller processing element can be any of a variety ofprocessors, such as, for example, the PIC17C752 microcontrollermanufactured by Microchip Technology Inc. The controller processingelement monitors and controls the functions of at least one, andpreferably multiple, solid-state switches 70, discussed below. Not onlydoes the controller processing element monitor and control the functionsof the switches, the controller processing element also determines acondition of the switches and/or loads by performing calculations in thefirmware using preconfigured characteristics and measured parameters ofthe switches and/or loads. The controller processing element allows theprogrammable controller to provide flexibility to the power system ofthe present invention not available with conventional circuit breakersor relays. By emulating the material limitations of conventional circuitbreakers and relays with firmware, the controller processing element ofthe programmable controller overcomes the material limitations ofconventional circuit breakers and relays, by having the capability toreprogram the controller processing element for different loads, asopposed to changing discrete components (i.e., conventional circuitbreakers and relays). Also, the programmable controller allows for awide variety of power control implementations to be programmed and madeselectable by the system, such as various trip-curve implementations. Inaddition, the controller processing element can caution an operator if adangerous condition is encountered, or the controller processing elementcan automatically control the respective switch accordingly.

The programmable controller 10 also includes at least one, andpreferably more than one, solid-state switch 70, each connected to arespective load 14. While the illustration of FIG. 7 depicts only asingle solid-state switch, it should be understood that the figure isfor illustrative purposes only, and should not be taken to limit thescope of the present invention. In one embodiment, illustrated in FIG.8, each solid-state switch includes a switching element 80, a driveelement 78 and a switch-protection element 76. While the switchingelement can comprise any number of different solid-state switches, suchas a MOSFET or an IGBT, the switching element acts to alter the inputcurrent to the respective load, typically operating in either an on modewherein the switching element permits the respective load to receive theinput current, or an off mode wherein the switching element prevents therespective load from receiving the input current. As previously stated,a solid-state switch eliminates the mechanical contacts of conventionalcircuit breakers and relays which, in turn, eliminates the erosion andother problems associated with mechanical contacts.

The solid-state switch 70 also includes a drive element 78 that providesthe input current to the switching element 80, and typically comprisescircuitry consisting of conventional electrical components such asresistors, diodes and transistors. Additionally, the solid-state switchmay include a switch-protection element 76 that protects the switchingelement against instantaneous over-current conditions that could damagethe switching element. The switch-protection element can comprise any ofa number of different configurations, but, like the drive element,typically comprises conventional electrical components such as diodes,transistors, resistors and capacitors.

In operation, the switch-protection element 76 senses an actual currentthrough the switching element 80. If the actual current is above apredetermined value, such as a maximum current rating of the switchingelement, the switch-protection element alters the actual current throughthe switching element so that the actual current is no more than thepredetermined value, typically placing the switching element in the offmode. In some instances when the solid-state switch 70 is initialized atstart-up, an inrush of actual current flows through the switchingelement. But while this current may be above the predetermined value, ittypically settles down to a level at or below the predetermined valuewithin a fairly short time. To account for this inrush of current andprevent the switch-protection element from prematurely altering theinput current, the switch-protection element of one embodiment iscapable of waiting a predetermined amount of time before monitoring thelevel of current through the switching element. This predeterminedamount of time allows the level of current to settle to a more constant,operation level before the switch-protection element monitors theswitching element for instantaneous over-current situations.Additionally, or alternatively, the switch-protection element can beconfigured to control the actual current in different manners atdifferent times or in different modes of operation. For example, theswitch-protection element can be configured to step down thepredetermined value at which current is interrupted from an initial,elevated value to a stable, constant value at the conclusion of thepredetermined amount of time.

Referring again to FIG. 7, the programmable controller 10 of the presentinvention includes at least one, and preferably more than one, measuringelement that measures various conditions of the loads 14 and solid-stateswitches 70. For example, the programmable controller may include acurrent measuring element 68 and/or a voltage measuring element 72 thatmeasure the input current through and voltage drop across a respectiveload. Additionally, the programmable controller may include atemperature measuring element 74 that measures the temperature at oraround the solid-state switch. The current and voltage measuringelements are typically made from conventional electrical components suchas resistors, capacitors and operational amplifiers. Also, thetemperature measuring device can be made from any number of devices,such as the LM75 digital temperature sensor, manufactured by NationalSemiconductor. In operation, the measuring elements protect the loads 14and/or solid-state switches 70 from undesirable conditions such asover-current, over and under voltage, and over and under temperatureconditions by comparing such measured parameters against predeterminedvalues for the respective load and/or switch. For example, thepredetermined value for each load may be based upon materialcharacteristics of the load, such as a maximum current or voltagerating, or a minimum operational voltage. Also, for example, thepredetermined temperature value for each solid-state switch may comprisea maximum temperature rating for the respective solid-state switch, overwhich damage is caused to the solid-state switch. Additionally, thepredetermined value based upon current or voltage rating characteristicscan additionally take into account the predetermined temperature valuebecause the current and voltage characteristics of various loadstypically change over a range of temperatures.

Referring to FIG. 9, typically, the controller processing element 66compares the measured parameters against the predetermined values byfirst constructing a model trip curve 82 comprising a plurality ofmeasured parameter values at different points in time. The controllerprocessing element compares the model trip curve against acharacteristic trip curve 84 for the respective load and/or switch. Thecharacteristic trip curve is typically predefined based upon acharacteristic of the switch and/or load associated with the particularparameter, such as a current rating characteristic trip curve associatedwith the measured input current through the switch and/or to the load.FIG. 9 illustrates a characteristic trip curve along with a constructedmodel trip curve for a switch and/or a load with a ten amp currentrating. Although not illustrated, the characteristic trip curve canadditionally be predefined based upon a combination of the variousparameters associated with the switch and/or load, such as thetemperature of the switch and/or load along with another parameter ofthe switch and/or load since many parameters of the switch and/or loadmay vary depending on the temperature of the switch and/or load. Thecharacteristic trip curve is stored by the controller processing elementor an associated memory device, thus making any trip curveimplementation possible, such as I²T and tiered. The predeterminedvalues of the characteristic trip curve are defined to prevent thesolid-state switch and/or load from operating too long in a dangerousarea 88. By referencing the characteristic trip curve, the controllerprocessing element can keep the measured parameter in a safe area 90,such as below the current rating of the switch and/or the load, and turnoff the switch before the switch and/or load can be damaged by crossinga critical point 86 on the characteristic trip curve. If the conditionmeasured by the respective measuring element falls outside the range ofpredetermined values or above the predetermined value or, moretypically, if the model trip curve constructed by the controllerprocessing element based upon the measured parameter or parameters ispredicted to reach the critical point on the characteristic trip curve,the controller processing element alters the input current through thesolid-state switch accordingly. For example, if the controllerprocessing element in conjunction with the measuring element determinethat the input current to the load will remain at or above a certainlevel for more than the maximum time permitted by the characteristictrip curve within a predefined period of time, the controller processingelement can alter the input current to bring the measured value withinthe predetermined value range or below the predetermined value or,preferably, the controller processing element can place the solid-stateswitch in the on or off mode.

In another advantageous embodiment, when the input current to the switchand/or the load reaches or exceeds a certain level, such as a maximumcurrent rating or an input current rating, respectively, the controllerprocessing element repeatedly increases a count. If the count exceeds apredetermined threshold representative of the predefined period of time,the controller processing element can alter the input current to reducethe input current to below the certain level, such as by placing theswitch in the off mode. But if the input current to the load decreasesto below the certain level before the count exceeds the threshold, thecontroller processing element will repeatedly decrease the count. Inthis regard, the controller processing element can account for previouscurrent stress (e.g., excess current) to the switch and/or the loadshould the switch and/or the load experience a subsequent current stressbefore the count reaches zero since the count would begin upward again,although not from zero but from a value representative of the residualstress on the switch and/or the load.

Referring now to FIGS. 10A, 10B and 10C, a method of remotelycontrolling the input current from the controller processing element 66through each switch 70 to each load 14, according to one embodiment ofthe present invention, begins by configuring the firmware of thecontroller processing element based upon the desired characteristics ofthe switches and loads, such as current and voltage ratings of eachload, a maximum current rating of each switch and/or a temperaturerating of each switch, as shown in block 100. For example, the firmwarecan be configured with the characteristic trip curves typicallypredefined based upon the characteristics of the switch and/or load.Additionally, the characteristic trip curves can be predefined basedupon a combination of the various characteristics of the switch and/orload, such as the temperature of the switch and/or load along withanother parameter of the switch and/or load since many parameters of theswitch and/or load may vary depending on the temperature of the switchand/or load. Thus, different characteristic trip curves can be utilizeddepending upon the temperature of the switch. Additionally, oralternatively, the characteristics of each switch related to currentthrough the switch, such as the maximum current rating, can beconfigured into the respective switch-protection element 76 to monitorthe actual current through the respective switch. Advantageously, byconfiguring the controller processing element with the characteristicsof the switches and loads, if a switch or load with differentcharacteristics is connected to the power system, the controllerprocessing element can be reconfigured such as by constructing andstoring the characteristic trip curves associated with the differentswitch or load, as opposed to replacing the discrete components ofconventional circuit breakers and relays.

After the controller processing element 66 has been configured, thedamaged wire detector 16 b can operate to determine whether any of theconductors are damaged and, if so, determine the location of the damage.Referring now to FIG. 10B, a method of detecting and locating eachdamage in each conductor begins by transmitting a set of test pulses,such as a set of 1 microsecond, 5 volt analog pulses, down theconductors, as shown in block 122. The comparator 68 can then receivereflections of the test pulses, and thereafter compare the analogreflections to an analog threshold voltage, as shown in block 124. Inthis regard, the comparator preferably compares the reflection of eachtest pulse to a threshold signal of a different magnitude, such as bycomparing the test pulses to threshold signals ranging from +7 volts to−7 volts in approximately 0.78 volt increments.

The digital data output of the comparator 68, which is representative ofthe reflections, can then be compared to reference digital data todetermine whether the digital data is within a threshold of thereference digital data. More particularly, the time required for eachtest pulse to travel down the conductors and reflect back can bedetermined from the digital data, which can thereafter be converted to adistance. The distance can then be compared against a reference distancedetermined from the reference digital data to thereby determine if thedistance determined from the digital data is lengthwise within athreshold of the reference distance. In this regard, the referencedigital data can be representative of reflections from known properlyoperating conductors of the same length and makeup as the conductorstested, as shown in block 126. The reference digital data can begenerated in any of a number of different manners but, in oneembodiment, the reference digital data is generated by training thedamaged wire detector 16 b using the conductors at an instance in whichit is known that the conductors are functioning properly, such as justafter configuring the programmable controller 10 with the damaged wiredetector and the loads 14. The threshold can equally be set in any of anumber of different manners. In one embodiment, for example, thethreshold is set at five percent of the reference digital data (i.e.,the distance determined from the digital data is within five percent ofthe distance determined from the reference digital data).

During the comparison, if the digital data is within a threshold of thereference digital data, the conductor is considered to be functioningproperly without any damage. Thereafter, a determination is made as towhether all of the conductors have been tested for damage, as shown inblock 130. If all of the conductors have not been tested, anotherconductor is selected, as shown in block 132. The process can thenrepeat for the next conductor, beginning with issuing the test pulsesdown the next conductor, as shown in block 122.

If the digital data is not within the threshold of the reference digitaldata, the processing element 40 can store the digital data and reportthe damaged conductor, such as to the programmable controller 10. In amore typical embodiment, however, if the digital data is not within thethreshold of the reference digital data, the one or more subsequenttests are performed on the same conductor to verify the damage to theconductor. In this regard, if the digital data is not within thethreshold of the reference digital data, the processing elementdetermines whether a predetermined number of passes (e.g., two) havebeen taken at the respective conductor, as shown in block 134. In otherterms, the processing element determines if the respective conductor hasfailed the test a predetermined number of times by failing to be withinthe threshold of the reference digital data during any such test. If thepredetermined number of passes have not been taken, the process canrepeat for the respective conductor, such as beginning with issuing thetest pulses, as shown in block 122.

If the predetermined number of passes have been taken and damage hasbeen detected with each pass, however, the processing element 40 canstore the digital data and report the damaged conductor (FAULT ALERT),as shown in block 136. As will be appreciated, if the programmablecontroller 10 receives notification that a conductor is damaged, such asby the digital data for the respective conductor not being within thereference digital data after a predetermined number of passes, theprogrammable controller will typically prevent current from beingapplied to the respective conductor, as such is described above.

After testing the conductors with the damaged wire detector 16 b, if thedamaged wire detectors do not detect a damaged conductor, each switch 70is operated in the on mode, as desired, to provide the input current tothe respective load 14, as shown in block 102 of FIG. 10A. As the switchis operating in the on mode, the switch-protection element senses theactual current through the switch, as illustrated in block 104. If theactual current is above a predetermined value, such as the maximumcurrent rating of the switch, the switch-protection element can wait apredetermined amount of time to allow any inrush of current to settle toa stable level, as shown in blocks 106 and 108. Additionally, oralternatively, the switch-protection element can be configured tocontrol the actual current at different times or in different modes ofoperation. For example, the switch-protection element and/or controllerprocessing element can be configured to step down the predeterminedvalue from an initial, elevated value to a stable value at theconclusion of the predetermined amount of time. If, after thepredetermined amount of time the actual current is still above thepredetermined value, the switch-protection element reduces the actualcurrent, such as by placing the switch in the off mode, as shown inblocks 111 and 120). In the event the actual current is below thepredetermined value, either initially or after the predetermined periodof time, the switch-protection element continuously monitors the actualcurrent to ensure the actual current remains below the predeterminedvalue, as shown in blocks 110 and 111.

As the switch-protection element 76 monitors the switch 70 for anover-current situation, the controller processing element 66periodically samples the current and/or voltage through and/or acrossthe load 14, and/or samples the temperature of or around the switch touse to obtain a condition of the load and/or switch, as illustrated inblock 112. The condition is then determined by comparing the current,voltage and/or temperature against the characteristics predefined by thecontroller processing element.

The controller processing element 66 can determine if an overtemperature or under temperature condition exists in the switch, asshown in block 114. And if so, the controller processing element canalter the input current accordingly. For example, the temperaturemeasuring element can measure the air temperature at or around theswitch and compare the measured temperature against the predeterminedvalues for the desired temperature range, such as critical temperaturelimits. If the measured temperature is below or above the desiredtemperature range, the controller processing element can place therespective switch in the off mode to prevent the switch from beingdamaged or from damaging the respective load, as shown in block 120.Alternatively, the controller processing element can construct differentcharacteristic trip curves based upon other parameters to emulate thetemperature at or around the switch based upon characteristics of theswitch that vary in proportion to the temperature of the switch.

The controller processing element 66 can also determine if an overvoltage or under voltage condition exists in the load 14 and alter theinput current accordingly, as shown in block 116. For example, if themeasured voltage drop across a respective load falls outside thepreconfigured voltage range for the respective load, the controllerprocessing element can alter the input current to place the voltage dropwithin the desired levels or place the respective switch 70 in the offmode.

The controller processing element 66 can also determine if an overcurrent condition exists in the load 14 and, if so, alter the inputcurrent to below the predetermined level, as shown in block 124. Forexample, the controller processing element can determine a model tripcurve 82 using a plurality of measured parameter values at differentpoints in time. The controller processing element compares the modeltrip curve against the characteristic trip curve 84 for the respectiveload and/or switch 70. The predetermined values in the characteristictrip curve are defined to prevent the switch from operating too long inthe dangerous area 88. Additionally, the controller processing elementcan account for previous current stresses (e.g., previous switchoperations in the dangerous area) by maintaining a count. As the switchoperates in the dangerous area, the controller processing elementrepeatedly increases the count. And if the switch returns to operatingoutside of the dangerous area before the count reaches a predeterminedthreshold (representative of the maximum amount of time the switch isallowed to operate in the dangerous area), the controller processingelement can repeatedly decrease the count as long as the switch remainsoutside the dangerous area, as previously described. By referencing thecharacteristic trip curve, the controller processing element can turnoff the switch before the switch and/or load can be damaged, such as byplacing the switch in the off mode, as shown in block 120.

In addition to monitoring for over or under temperature, voltage orcurrent conditions, the arc fault detector 16 a and the ground faultcircuit interrupt 16 c, can operate to further insure proper operationof the conductors. Although shown and described herein as operatingwhile input current is provided to the loads, the arc fault detector andground fault circuit interrupt can equally operate at any other timesignals are transmitted through the conductors, including duringoperation of the damaged wire detector 16 b, without departing from thespirit and scope of the present invention.

More particularly, as the switch 70 is operating in the on mode, the arcfault detector 16 a continuously monitors the output current of theprogrammable controller 10 for characteristics identifying an arc event,such as in a manner described above and as shown in block 140. If thearc fault detector detects an arc event, then, the arc fault detectorcan notify the programmable controller, which can respond by placing theswitch in the off mode, as shown in block 142. However, the damaged wiredetector 16 b can also, but need not, be operated to verify the electricarc event during its presence and, if verified, locate the electric arcevent, such as in a manner shown in FIG. 10B. If the arc fault detectordoes not detect an arc event, however, the arc fault detector cancontinue to monitor the output current of the programmable controllerfor characteristics identifying a potential arc event.

The ground fault circuit interrupt 16 c can detect stray currents on theconductors that may indicate a short circuit in one of the conductorsand/or an electric arc event. In this regard, the ground fault circuitinterrupt can operate by initially receiving a measurementrepresentative of the current difference between the pair of conductorsto the loads, as such may be determined by passing the currents throughthe sensing coil 62, as shown in block 144. After receiving themeasurement, the measurement can be compared to a predefined threshold,as shown in block 146. As indicated above, if the currents in theconductors are exactly equal, then, a net current of zero will beeffected in the sensing coil. However, as the sensing coil produces anAC magnetic field external to the conductors, a non-zero net current inthe conductors would induce a voltage in the sensing coil.

Therefore, if the current difference in the conductors does not exceedthe predefined threshold, the ground fault circuit interrupt 16 ctypically takes no action with respect to the programmable controller10. Instead, the ground fault circuit interrupt repeats the technique byagain receiving a measurement representative of the current differencein the conductors. The ground fault circuit interrupt can thereforerepeatedly receive measurements and compare the measurements to thepredefined threshold to attempt to detect a short circuit and/orelectric arc event, as evidenced by a difference in the current in theconductors exceeding the predefined threshold.

If the current difference in the conductors exceeds a predefinedthreshold, the ground fault circuit interrupt 16 c can notify theprogrammable controller 10. In turn, the programmable controller canoperate to prevent current from reaching the loads 14, such as byoperating the switch 70 in the off mode, as shown in block 142. Then,the damaged wire detector 16 c can, but need not, test the conductors,such as according to the technique described above in conjunction withFIG. 10B.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

1. A system of remotely detecting and locating faults in a power system,said system comprising: at least one slave controller disposed proximateat least one load and electrically connected to the at least one loadvia at least one conductor, wherein the at least one slave controllercomprises: at least one solid-state switch capable of controllablyaltering the input current to the at least one load; and at least onemeasuring element for measuring at least one parameter associated withthe at least one load and the at least one solid-state switch, whereinsaid solid-state switch controllably alters the input current to the atleast one load according to the at least one parameter; and at least onesupplemental protection module electrically connected to the at leastone conductor between the at least one slave controller and the at leastone load, wherein the at least one supplemental protection module iscapable of detecting at least one fault in at least one conductor.
 2. Asystem according to claim 1, wherein each supplemental protection moduleis capable of notifying a respective slave controller when thesupplemental protection module detects a fault such that the at leastone solid-state switch of the respective slave controller can alter theinput current to the at least one load.
 3. A system according to claim1, wherein the at least one solid-state switch operates in at least onemode selected from a group consisting of an on mode wherein the at leastone solid-state switch permits a respective load to receive the inputcurrent, and an off mode wherein the at least one solid-state switchprevents the respective load from receiving the input current, andwherein when the at least one solid-state switch operates in the offmode the at least one supplemental protection module is capable oftesting the at least one conductor before the at least one solid-stateswitch is placed in the on mode to thereby detect at least one fault. 4.A system according to claim 1, wherein each supplemental protectionmodule is capable of detecting at least one fault comprising at leastone damaged conductor by: transmitting at least one test pulse along atleast one respective conductor and receiving at least one reflectionfrom the at least one respective conductor; and comparing the at leastone reflection to reference data to thereby at least one of detect andlocate at least one damaged conductor.
 5. A system according to claim 4,wherein each supplemental protection module is further capable ofdetecting at least one damaged conductor by converting the at least onereflection to digital data representative of the at least onereflection, and wherein each supplemental protection module is capableof comparing the at least one reflection to reference data by comparingthe digital data to the reference data.
 6. A system according to claim5, wherein each supplemental protection module is capable of convertingthe at least one reflection to digital data with at least oneresolution.
 7. A system according to claim 4, wherein each supplementalprotection module is further capable of determining at least one lengthof the at least one conductor based upon at least one transit timebetween transmission of the at least one test pulse and reception of therespective at least one reflection, and wherein each supplementalprotection module is capable of comparing the at least one reflection toreference data by comparing the at least one determined length to atleast one reference length.
 8. A system according to claim 7, whereineach supplemental protection module is capable of comparing the at leastone determined length to the at least one reference length and detectingat least one damaged conductor when the at least one determined lengthis shorter than the respective at least one reference length by morethan a threshold length, and wherein each supplemental protection moduleis capable of locating the damage as a point on the respective at leastone conductor at the at least one determined length.
 9. A systemaccording to claim 1, wherein each supplemental protection module iscapable of detecting at least one fault comprising an electric arc eventby detecting at least one of white noise and chaotic behavior in currentthrough the at least one conductor to the at least one load.
 10. Asystem according to claim 9, wherein each supplemental protection moduleis capable of detecting white noise by detecting a spectrally densecurrent through the at least one conductor to the at least one load. 11.A system according to claim 9, wherein each supplemental protectionmodule is capable of notifying a respective slave controller when thesupplemental protection module detects an electric arc event such thatthe at least one solid-state switch of the respective slave controllercan alter the input current to the at least one load to prevent therespective load from receiving the input current, and wherein when therespective slave controller alters the input current to prevent therespective load from receiving the input current the respectivesupplemental protection module can at least one of verify the electricarc event and locate the electric arc event on the respective conductor.12. A system according to claim 1, wherein each supplemental protectionmodule is capable of detecting at least one fault comprising at leastone abnormal current representative of at least one of a short circuitand an electric arc event.
 13. A system according to claim 12, whereineach conductor comprises a pair of conductors, and wherein eachsupplemental protection element is capable of detecting at least onefault by: receiving a measurement representative of a current differencein the pair of conductors; and comparing the measurement to a predefinedthreshold such that the supplemental protection element is capable ofdetecting an abnormal current representative of a short circuit when themeasurement is greater than the predefined threshold.
 14. A systemaccording to claim 12, wherein each supplemental protection module iscapable of notifying a respective slave controller when the supplementalprotection module detects at least one abnormal current representativeof at least one of a short circuit and an electric arc event such thatthe at least one solid-state switch of the respective slave controllercan alter the input current to the at least one load to prevent therespective load from receiving the input current, and wherein when therespective slave controller alters the input current to prevent therespective load from receiving the input current the respectivesupplemental protection module can at least one of verify the at leastone abnormal current representative of at least one of a short circuitand an electric arc event and locate at least one of the short circuitand the electric arc event on the respective conductor.
 15. A method ofremotely detecting at least one fault in a power system comprising:configuring a processing element that controls input current through atleast one switch to at least one load via at least one conductor,wherein the configuring is based upon at least one characteristicselected from a group consisting of a current rating of each load, avoltage rating of each load, a maximum current rating of each switch anda temperature rating of each switch; operating each switch in an offmode wherein each switch prevents the input current from flowing to arespective load; testing the at least one conductor to thereby detect atleast one fault in the at least one conductor; operating each switch inan on mode wherein each switch permits the input current to flow to arespective load when no damaged conductors are detected, and thereaftercontrolling the input current to the at least one load, whereincontrolling the input current comprises: monitoring at least oneparameter associated with each switch and respective load selected froma group consisting of the input current to the load, a voltage dropacross the load, the input current through the switch and a temperatureof the switch; determining a condition of each switch and respectiveload depending upon at least one of the at least one characteristic andthe at least one parameter; monitoring the at least one conductor tothereby detect at least one fault in the at least one conductor; andoperating each switch in at least one mode selected from a groupconsisting of the on mode and the off mode depending upon the conditionof the respective loads and at least one fault in the at least oneconductor.
 16. A method according to claim 15, wherein testing the atleast one conductor comprises: transmitting at least one test pulse downat least one respective conductor and receiving at least one reflectionfrom the at least one respective conductor; and comparing the at leastone reflection to reference data to thereby at least one of detect andlocate at least one damaged conductor.
 17. A method according to claim16, wherein testing the at least one conductor further comprisesconverting the at least one reflection to digital data representative ofthe at least one reflection, and wherein comparing the at least onereflection to reference data comprises comparing the digital data to thereference data.
 18. A method according to claim 17, wherein convertingthe at least one reflection comprises converting the at least onereflection to digital data with at least one resolution.
 19. A methodaccording to claim 16, wherein testing the at least one conductorfurther comprises determining at least one length of the at least oneconductor based upon at least one transit time between transmission ofthe at least one test pulse and reception of the respective at least onereflection, wherein comparing the at least one reflection to referencedata comprises comparing the at least one determined length to at leastone reference length.
 20. A method according to claim 19, whereincomparing the at least one determined length to the at least onereference length comprises detecting at least one damaged conductor whenthe at least one determined length is shorter than the respective atleast one reference length by more than a threshold length, and whereinlocating the at least one damaged conductor comprises locating a pointon the respective at least one conductor at the at least one determinedlength.
 21. A method according to claim 15, wherein monitoring the atleast one conductor to thereby detect at least one fault comprisesmonitoring the at least one conductor to thereby detect an electric arcevent by detecting at least one of white noise and chaotic behavior incurrent through the at least one conductor to the at least one load. 22.A method according to claim 21, wherein detecting white noise comprisesdetecting a spectrally dense current through the at least one conductorto the at least one load.
 23. A method according to claim 21, whereinoperating each switch comprises operating at least one switch in the offmode when an electric arc event is detected on at least one conductor,and wherein the method further comprises testing the at least oneconductor after operating the at least one switch in the off mode tothereby at least one of verify the electric arc event and locate theelectric arc event on the respective at least one conductor.
 24. Amethod according to claim 15, wherein monitoring the at least oneconductor to thereby detect at least one fault comprises monitoring theat least one conductor to thereby detect at least one abnormal currentrepresentative of at least one of a short circuit and an electric arcevent.
 25. A method according to claim 24, wherein each conductorcomprises a pair of conductors, and wherein monitoring each of the atleast one conductor comprises: receiving a measurement representative ofa current difference in the pair of conductors; and comparing themeasurement to a predefined threshold, wherein an abnormal current isdetected when the measurement is greater than the predefined threshold.26. A method according to claim 24, wherein operating each switchcomprises operating at least one switch in the off mode when at leastone abnormal current representative of at least one of a short circuitand an electric arc event is detected on at least one conductor, andwherein the method further comprises testing the at least one conductorafter operating the at least one switch in the off mode to thereby atleast one of verify the at least one abnormal current representative ofat least one of a short circuit and an electric arc event and locate atleast one of the short circuit and the electric arc event on therespective at least one conductor.